This invention relates generally to fluid powered devices and more particularly to a fluid powered, part locator.
It is known to employ automatically powered locating pins which are moved from retracted positions to advanced positions to engage and locate workpiece parts on an assembly line or checking station. For example, one conventional pin part locator employs a pneumatically driven piston, having an oval peripheral shape, which advances and retracts an elongated piston rod connected to a tapered workpiece locating pin. However, the tolerances and accuracy of the piston rod and locator pin relative to the body are poor and can vary by as much as plus or minus one-half degree from the desired centerline. This type of inaccuracy is even further accentuated when employed to locate or orient sheet metal panels on an automotive vehicle assembly line when a small tolerance mismatch at the bottom of the vehicle may accumulate to a considerable tolerance stack-up at the vehicle""s roof.
It is also known to use proximity switches with pneumatically powered industrial devices such as pin part locators, powered clamps and robotic grippers. For example, reference should be made to U.S. Pat. No. 5,190,334 entitled xe2x80x9cPowered Clamp with Parallel Jawsxe2x80x9d which issued to Sawdon on Mar. 2, 1993, and U.S. Pat. No. 5,871,250 entitled xe2x80x9cSealed Straight Line Gripperxe2x80x9d which also issued to Sawdon on Feb. 16, 1999; these patents are incorporated by reference herein. It is noteworthy, however, that the proximity switches are mounted in optional fluid ports and protrude externally from the devices, thereby requiring additional assembly line clearance.
In accordance with the present invention, a preferred embodiment of a fluid powered apparatus has a housing, a piston and an off-axis member to deter piston rod rotation relative to the housing. In another aspect of the present invention, the member is a finger extending between the piston rod and the piston. In a further aspect of the present invention, the member is an off-center pin aligning the piston and the housing. Still another aspect of the present invention employs an off-center pin projecting from both opposed faces of the piston for removably projecting into opposed holes in the housing on either side of a fluid chamber. In yet a further aspect of the present invention, an off-center pin actuates one or more sensors while also deterring rotation of a piston rod relative to a housing. An additional aspect of the present invention provides for complete retention and sealing of a sensor within a housing.
The apparatus of the present invention is advantageous over conventional devices in that the present invention is significantly more compact and precise. When used with a pin part locator, the compactness allows for reduced component dimensions and closer proximity of the actuating components to the workpiece; this increases precise repeatability and improves tolerance stack-ups within the apparatus. The compactness is enhanced by the multiple functionality of the off-center pin and sensor packaging. Furthermore, the tolerance stack-ups within the apparatus are improved by the multiple anti-rotation features employed as well as positive seating of the piston rod and piston relative to the housing. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.